Torsion and bending of braced thin-walled open sections

Abstract A theoretical and experimental study of the torsional and flexural properties of braced, thin-walled, open sections, such as elevator core shear walls in tall buildings, with lintel beams across the openings at each storey level, is described. The theoretical model developed is consistent with established open-section and closed-section behaviour at the two extremes of bracing, and takes into account the bending and shear deformation of the bracing beams, out-of-plane bending of the side walls and continuous shear flow around the contour of the assumed equivalent closed section. Theoretical results are compared, and show close agreement, with experiments on perforated, extruded, aluminium tubes. The results indicate a significant increase in torsional stiffness when distortion of the side walls is restrained by the presence of channel lips.